Dogwood tree named ‘Rutnut’

ABSTRACT

A cultivar of dogwood tree is characterized by a unique combination of red floral bracts and a dwarf rounded shape.

Latin name of genus and species: Cornus florida L. var. rubra West.

Cultivar name: ‘Rutnut’.

BACKGROUND OF THE INVENTION

This new cultivar is the product of a long standing detailed program ofhybridization and selection of large-bracted dogwoods, in this instancefrom our native Eastern or Cornus florida seedlings which are carefullycontrolled, records carefully retained and characteristics analyzed fortheir differences and outstanding value as potential commercialvarieties or cultivars.

As will be understood from the following, the program has resulted inmany outstanding crosses which ultimately result in particularlyattractive vegetative and floral parts, which appear on trees which arevery floriferous and regular bearers.

We have selected the particular seedling hereof from certain progenygrown in a cultivated area and, as a result, have in turn caused thesame to be asexually reproduced by stem cuttings in the vicinity of NewBrunswick, N.J. The cultivar may also be so reproduced by budding andgrafting. The claimed cultivar is stable and reproduced true to type insuccessive generation of asexual reproduction.

The reproduction and actual growth and selection of the new cultivartook place in the vicinity of New Brunswick, N.J. and has been found tobe distinctive as to its winter-hardiness in that area, USDA PlantHardiness Map Zone 6a.

As will be understood from the detailed description of the inventionwhich appears hereinafter, the new cultivar is in fact outstanding andreadily identified as being such, thus providing for a new variety whichis identified botanically for the purposes hereof as Cornus florida L.Var. rubra West, and will be known commercially as ‘Rutnut’.

With the foregoing in mind, the description which follows will beunderstood as clearly defining the new cultivar, the desirablecharacteristics of which are the result of such a program as has beenheretofore suggested.

SUMMARY OF THE INVENTION

A cultivar of dogwood tree that is characterized by a unique combinationof red floral bracts and a dwarf rounded shape. This new variety isdistinguished from its parents, both of which grew to heights of 5 to 7meters and exhibited flower heads with white bracts, whereas plants of“Rutnut” at maturity are very dwarf in size (less than 1 meter). It isbelieved to be the only dwarf Cornus florida to produce flower headsexhibiting pink-red floral bracts.

BRIEF DESCRIPTION OF THE DRAWINGS

This new cultivar of dogwood is illustrated by the accompanyingphotographic drawings, depicting the plant by the best possible colorrepresentation using color photography. All color references below aremeasured against The Royal Horticultural Society (R.H.S.) Colour Chart.Colors are approximate as color depends on horticultural practices, suchas light level and fertilization rate, among others.

FIG. 1 is a two-year liner showing the dwarf nature of the tree and itsprecocious floral display of dark red floral bracts; and

FIG. 2 discloses several flower heads at the time of floral display andindicates the color and shape of the floral bracts.

BOTANICAL DESCRIPTION OF THE INVENTION

Origin: A seedling selection from the progeny of a controlled cross oftwo select seedlings, each of which originated from a cross of a plantof C. florida var. rubra×a plant of C. florida ‘Pygmy’ (a white-bracted,non-patented cultivar), the rubra plants in the two initial crossesbeing unrelated in origin. Unpatented. Not subject of pending U.S. plantpatent applications. Staminate parent of each parental hybrid was thecultivar ‘Pygmy’ (non-patented).

Reproduction took place in the vicinity of New Brunswick, N.J.

Classification: Botanic name: Cornus florida L. var. rubra West.Commercial name: ‘Rutnut’.

Tree: Dwarf and rounded in shape. Is the first truly dwarf cultivar ofvar. rubra to be introduced to commerce, a five-year tree typicallybeing 0.71 M tall and 0.61 M wide, or approximately one-half the typicalsize of a five-year plant of ‘D-376-15’, a patented (U.S. Plant Pat. No.8,214) red-bracted clone of C. florida which develops a rounded, compacthabit of growth considered semi-dwarf relative to standard clones(unpatented) of Cornus florida var. rubra, such as ‘Sweetwater’, ‘SpringSong’, ‘Prosser Red’, and the patented rubra clone ‘Cherokee Chief’,U.S. Plant Pat. No. 1,710 as well as white-bracted cultivars, such as‘Cherokee Princess’ and ‘Springtime’. Vegetative and floral parts havebeen fully winter-hardy at New Brunswick, N.J., USDA Plant HardinessZone 6a. Very floriferous. Regular bearer. A five-year plant of ‘Rutnut’is about 76-91.5 cm tall with a spread of 61 cm in comparison to thewhite-bracted, non-patented cultivar ‘Pygmy’ which at five yearsaverages 61-76 cm tall with a spread of 45.7 cm.

Trunk: Smooth as a young plant but bark becomes shaggy with age as istypical for plants of C. florida. Color of trunk or bark is 199D (GreyedGreen Group on the R.H.S. Colour Chart of The Royal HorticulturalSociety, London).

Branches: Smooth, small to medium, with a high number of side brancheswhich causes the tree to be dwarf and rounded; older branches ranging incolor from 165A (Greyed Orange Group) to 200A (Brown Group); new tipgrowth being 146A (Yellow-Green Group).

Leaves:

Ovate, with broadly attenuate base and apiculate tip.—Length 6.3 to 12.2cm (ave.=10.4 cm). Width at widest point 4.1 to 7.3 cm (ave.=6.01 cm).Petiole length 8 to 18 mm (ave.=12); Width 12 mm. Number of primaryveins per leaf 10-12 (ave.=10.9). Margins entire.

Color.—Upper surface is closest to 137A (Green Group) but slightlydarker. Lower surface is between 138B and 138C (Green Group); lowersurface contains minute white pubescence, slightly longer along veinsthan on remainder of surface.

Fall color.—Typical of most C. florida, a showy display of green,yellow, orange and a red which is typical of most rubra varieties.

Flower buds: Medium size, nearly globose — height and width range from4.0-5 mm. True flowers are tiny and relatively inconspicuous (each withfour minute petals that are greenish-white in color). They are borne indense heads, and are enclosed over winter by four involucral bracts thatsubtend the true flowers. Plants of ‘Rutnut’ are self-incompatible, asare all plants of C. florida.

Involucral, or floral bracts:

Color.—When fully expanded: Upper surface 59C to 59D (Red-Purple Group);lower surface 59D (Red-Purple Group). Basal 10% of bract surface isWhite Group 155D.

Size and shape.—When the floral bracts are fully expanded, the diameterof the involucre from tip to tip of the opposing inner bracts is about7.53 cm. The diameter of the involucre as measured from tip to tip ofthe opposing outer bracts is approximately 7.11 cm. The average lengthof the inner and outer bracts is about 3.59 cm and 3.38 cm,respectively. The width of the inner and outer bracts at their widestpoint is about 2.71 cm and 3.59 cm, respectively. In general, the outerbracts are nearly equal in length and width and are broadly tapered atthe base, whereas the inner bracts are longer than wide and are morenarrowly tapered at the base. In general, the floral bracts would beconsidered obovate with an abruptly acute tip. The margin of the floralbracts is entire. The surface of the floral bracts has a soft ridgedtexture due to the prominent parallel veination. The basal one-third ofadjacent bracts slightly overlap.

Peduncle: Each flower head is borne on a peduncle, the average length ofwhich is about 2.15 cm at the time of flowering and/of floral display.The average peduncle length will vary slightly from year to year. Coloris Green Group 137D.

Flowering and floral display: The period of floral display (floralbracts) is typical of that for most plants of C. florida; i.e.,occurring in late April and early May in the vicinity of New Brunswick,N.J., and extending for a period of 12-17 days, depending on weatherconditions. Anthesis of the tiny, relatively inconspicuous, true flowerscommences two to four days after the onset of the ornamental display ofthe large floral bracts and continues for about seven days, depending onweather conditions. The average number of true flowers per flower headin our new intraspecific hybrid is about 14.7, whereas those of thepatented clone ‘D-376-15’, which also bears red bracts (184C,Grey-Purple Group), is about 19.7. This characteristic is quiteconsistent from year to year. The mature size of ‘Rutnut’ is expected tobe about one-half that of ‘D-376-15’; i.e. about 1.7 m tall and 1.7 mwide. The flower has no detectable fragrance. Average flower headdiameter of over-wintering flower buds is 3 mm. Average diameter offlower head at start of flowering period is 4-6 mm. Flower petals: fourper flower. Length: about 2 to 3 mm. Width: about 1.25 mm. Apex:rounded. Margin: Entire. Color: Just prior to anthesis, both surfacesYellow-Green Group 144C. Fully open, both surfaces Yellow-green Group151D.

Reproductive organs: Features are inconspicuous. Ovary: inferior andbilocular with each locule having one ovule. Length: about 9 mm. Width:about 6 mm; Style is about 1.75 to 2.25 mm in length and 0.25 mm indiameter. The color of the style is closest to Yellow_Green Group 149A.Sepals: four per flower. Cannot be seen at the time of flowering unlessthe flower is dissected. Since the ovary is inferior, the sepals arereadily observed at the tip of the mature fruit in September. To thenaked eye, the sepals appear as equilateral triangles, each side ofwhich is about 1 mm in length. Under 10× magnification, the sides andtip of the sepals can be seen to be slightly rounded and the basal 20percent of adjacent sepals are fused. The color of the sepals on themature fruit is Brown Group 200A. Petals: four per flower. Length: about2 to 3 mm. Width: about 1.25 mm. apex: rounded. Margin: Entire. Color:Just prior to anthesis, both surface Yellow-Green Group 144C. Fullyopen, both surface Yellow-Green Group 151D. Stamens: Four per flower.Filament: Length: about 1.8 to 2 mm. Width: about 0.2 mm. Anther: Color:Yellow Group 11C. Pollen: closest to Yellow Group 11B.

Fruit: The fruit are elongate, approximately 9 to 13 mm long and brightred, RHS 45A and/or RHS 46B, (Red Group) as is rather typical of thefruit of most plants of C. florida. Fruit: Shape/type: Oblong drupe.Length: about 1.1 cm. Diameter: about 0.8 cm. Texture: Smooth. Color ofpericarp of fruit: Red Group 46B. Seeds: Shape ovoid. Texture:horizontal furrows on opposing sides clearly delineate the two locules.Color: Freshly cleaned and dried seed closest to Greyed-Orange Group146B.

Resistance to insects: The relative resistance, or susceptibility, ofplants of ‘Rutnut’ to the various insect pests known to attack plants ofC. florida is expected to be typical of that of plants of most cultivarsof C. florida.

Diseases: The relative resistance, or susceptibility, of plants of‘Rutnut’ to the various disease organisms known to attack plants of C.florida is assumed to be typical of that exhibited by most plants of C.florida but little information is available at this time.

We claim:
 1. A new and distinct cultivar of dogwood tree, substantiallyas herein shown and described, characterized particularly as to noveltyby the unique combination of its red floral bracts and the truly dwarfrounded habit of the tree.